Measuring device for determining a distance in a conducting structure

Abstract

The invention relates to a distance-measuring device for determining a distance between a reflection body in a conducting structure and a coupling region for electromagnetic waves, which region is provided on an end section of the conducting structure, said measuring device comprising a transmitting and receiving device, and a conduction junction ( 1 ) provided on the coupling region, for coupling the transmitting and receiving device to the conducting structure containing a medium, in order to couple an electromagnetic wave into the conducting structure, and to decouple the electromagnetic wave, reflected on the reflection body, from the conducting structure. Said measuring device also comprises an evaluation device for determining the distance between the coupling region and the reflection body from the complex reflection coefficient between the coupled electromagnetic wave and the decoupled electromagnetic wave. The invention also relates to the corresponding method.

The invention claimed is: 
     
       1. A distance measuring device for determining a distance between a piston and a coupling region in a cylinder, the distance measuring device comprising:
 a conduction junction at the coupling region; 
 a transmitting and receiving device configured to electromagnetically couple an electromagnetic wave into the cylinder and to decouple an electromagnetic wave reflected from the piston; 
 a transmission line for detecting material properties of a medium contained in the cylinder, the transmission line being positioned at the coupling region and comprising a coupling point and a decoupling point; and 
 an evaluation device configured to determine a distance between the coupling region and the piston based on material properties detected by the transmission line and on a complex reflection coefficient between the coupled electromagnetic wave and the decoupled electromagnetic wave. 
 
     
     
       2. The distance measuring device of  claim 1 , wherein the measuring transmission line is positioned to detect the material properties of the medium in the region of coupling into the cylinder for determining distance. 
     
     
       3. The distance measuring device of  claim 2 , further comprising evaluation electronics comprising an HF transmitter and an HF receiver, and wherein the measuring transmission line is operated in transmission, the measuring transmission line is connected to the HF transmitter of the evaluation electronics by a coupling structure, and the measuring transmission line is connected to the HF receiver of the evaluation electronics by a decoupling structure. 
     
     
       4. The distance measuring device of  claim 3 , wherein the distance measuring device is configured to measure a phase that corresponds to an electrical length of the measuring transmission line using the HF receiver and the HF transmitter connected to the measuring transmission line. 
     
     
       5. The distance measuring device of  claim 2 , further comprising evaluation electronics comprising an HF transmitter and an HF receiver, and the measuring transmission line is operated in reflection, the measuring transmission line is connected to the HF transmitter and the HF receiver of the evaluation electronics by a directional coupler, and the measuring transmission line has a reflection point. 
     
     
       6. The distance measuring device of  claim 1 , wherein the transmission line is a TEM line. 
     
     
       7. The distance measuring device of  claim 1 , wherein the transmission line is a coaxial line.